Creating a summary chart from a table of data

Thank you very much for your help. That's working for me now. I'm assuming for a stacked bar chart, I have to create specific data from the chart rather than field arguments to separate them?

You are right. It is necessary to add separate value fields to your data source to display the stacked bar diagram. In this case, you will be able to create several Stacked Bar series and bind them to these fields.
If this does not help, would you explain your main task in greater detail? We will then do our best to find an acceptable solution for you.

Well I have a relatively simple table which in the current chart is being shown as I want using the COUNT() function and the argument value is the employee ID. So as in my initial question I can easily see Employee A has 25 clients etc etc.
I only really need a minor modification (visually) to make this a standard bar chart to a stacked bar chart.
All the rows contain a boolean value indicating whether they are "in time" or "out of time" as it were. I was hoping to be able to make use of that to tell the chart to split the count if you see what I mean. The "stack" would never have more than two parts.
I'm really trying to avoid loading extra tables into datasets when the data is already present. Could I achieve what I want using e.g. two data views with filters applied and then each used for a series?
My final (!) requirement would be to have the colour of each bar in the chart the same as in the "colour" field of the row for "in time" clients and Cyan (our standard alert style colour) for the colour of the "out of time" clients. This is already how we display the same data in Grid Controls using style format conditions and in Schedulers using resources created at run time from a separate table and the event Custom Draw Appointment. This colour consistency across the entire application is very important.
I greatly appreciate your assistance with this.
Miles